Conventionally, a technology of conveying substrates such as wafers for manufacturing semiconductors by a robot is used broadly. Here, various processing steps such as a wafer cleaning process, a film-forming process, a heating process, and an etching process are executed when manufacturing semiconductors. The respective processing steps are executed by different processing devices respectively, and therefore wafers need to be conveyed between a plurality of processing devices.
A substrate conveyance robot used for conveying substrates such as wafer is configured for example by attaching a base end portion of a robot arm to a top end portion of a rotary spindle which can be elevated along a Z-axis, and mounting a hand as a substrate holding device to a distal end portion of the robot arm. The hand has a blade member on which a substrate is to be placed and held.
Then, when a substrate is taken out from the inside of a substrate storing container in which multiple substrates are stored, the rotary spindle and the robot arm are driven by a robot controller so as to advance the blade member of the hand between substrates stored in the container and position the blade member below a substrate to be conveyed. From this state, the rotary spindle is elevated and the substrate to be conveyed is placed on the blade member, and the substrate is fixed on the blade member by a substrate fix mechanism (such as edge grip mechanism and vacuum sucking mechanism) provided to the hand.
Subsequently, the robot arm and the rotary spindle are driven by the robot controller so as to draw the blade member together with the substrate from the container and the substrate is conveyed to a predetermined conveyance destination.
When a substrate is to be carried out from the container using the substrate conveyance robot as mentioned above, there are cases when work (mapping) for confirming the storing state of multiple substrates stored in the container (such as presence/absence of substrates) using a substrate detection sensor is performed.
This mapping work may be performed using a mapping mechanism installed separately from the substrate conveyance robot (Patent Document 1) or may be performed using a substrate detection sensor mounted to the substrate conveyance robot (Patent Document 2).
In the latter case, for example, an optical sensor is mounted to a distal end portion of the blade member of the robot hand and presence/absence of a substrate is determined based on a detection signal of the optical sensor. Thus, the rotary spindle to which the base end portion of the robot arm is mounted is elevated or lowered so as to make the distal end portion of the blade member of the robot hand scan along edge portions of multiple substrates arranged in the vertical direction.
Then, an output signal of the optical sensor is changed between the case when a substrate is present and the case when a substrate is not present in each slot of the substrate storing container. Thus presence/absence of a substrate in each slot is detected based on this output signal.
Additionally, also when presence/absence of a substrate in a processing device for processing a substrate, not in the substrate storing container, is detected, the rotary spindle and the robot arm are driven so as to insert the robot hand into the processing device, and the rotary spindle is elevated or lowered so as to make the distal end portion of the blade member scan along an edge portion of a substrate.
Also in this case, the output signal of the optical sensor is changed between the case when a substrate is present and the case when a substrate is not present in the processing device. Thus presence/absence of a substrate in the processing device can be detected based on this output signal.